Active LED driver of high PF and low THD compatible with rapid-start ballast

A new active LED driver with high power factor (PF) and low total harmonic distortion (THD) compatible with a conventional rapid-start ballast is proposed. A dedicated LC compensation circuit is attached to the ballast to increase the PF and lower the THD of the source current. A boost converter is used for regulating the LED current, however its duty cycle is bounded to avoid the unstable operating region, which is analyzed and characterized in this paper. A small DC input capacitor is used to prevent the ballast from an excessive transient voltage and current. The design of the active LED driver for the highly non-linear ballast is verified by extensive experiments.